/*
 * @(#)LogicalFunction.java
 *
 * Copyright 2003-2004 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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package org.wso2.balana.cond;

import org.wso2.balana.ctx.EvaluationCtx;

import org.wso2.balana.attr.AttributeValue;
import org.wso2.balana.attr.BooleanAttribute;

import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

/**
 * A class that implements the logical functions "or" and "and". These functions
 * take any number of boolean arguments and evaluate them one at a time,
 * starting with the first argument. As soon as the result of the function can
 * be determined, evaluation stops and that result is returned. During this
 * process, if any argument evaluates to indeterminate, an indeterminate result
 * is returned.
 * 
 * @since 1.0
 * @author Steve Hanna
 * @author Seth Proctor
 */
public class LogicalFunction extends FunctionBase {

	/**
	 * Standard identifier for the or function.
	 */
	public static final String NAME_OR = FUNCTION_NS + "or";

	/**
	 * Standard identifier for the and function.
	 */
	public static final String NAME_AND = FUNCTION_NS + "and";

	// internal identifiers for each of the supported functions
	private static final int ID_OR = 0;
	private static final int ID_AND = 1;

	/**
	 * Creates a new <code>LogicalFunction</code> object.
	 * 
	 * @param functionName
	 *            the standard XACML name of the function to be handled by this
	 *            object, including the full namespace
	 * 
	 * @throws IllegalArgumentException
	 *             if the functionName is unknown
	 */
	public LogicalFunction(String functionName) {
		super(functionName, getId(functionName), BooleanAttribute.identifier,
				false, -1, BooleanAttribute.identifier, false);
	}

	/**
	 * Private helper that looks up the private id based on the function name.
	 */
	private static int getId(String functionName) {
		if (functionName.equals(NAME_OR))
			return ID_OR;
		else if (functionName.equals(NAME_AND))
			return ID_AND;
		else
			throw new IllegalArgumentException("unknown logical function: "
					+ functionName);
	}

	/**
	 * Returns a <code>Set</code> containing all the function identifiers
	 * supported by this class.
	 * 
	 * @return a <code>Set</code> of <code>String</code>s
	 */
	public static Set getSupportedIdentifiers() {
		Set set = new HashSet();

		set.add(NAME_OR);
		set.add(NAME_AND);

		return set;
	}

	/**
	 * Evaluate the function, using the specified parameters.
	 * 
	 * @param inputs
	 *            a <code>List</code> of <code>Evaluatable</code> objects
	 *            representing the arguments passed to the function
	 * @param context
	 *            an <code>EvaluationCtx</code> so that the
	 *            <code>Evaluatable</code> objects can be evaluated
	 * @return an <code>EvaluationResult</code> representing the function's
	 *         result
	 */
	public EvaluationResult evaluate(List inputs, EvaluationCtx context) {

		// Evaluate the arguments one by one. As soon as we can
		// return a result, do so. Return Indeterminate if any argument
		// evaluated is indeterminate.
		Iterator it = inputs.iterator();
		while (it.hasNext()) {
			Evaluatable eval = (Evaluatable) (it.next());

			// Evaluate the argument
			EvaluationResult result = eval.evaluate(context);
			if (result.indeterminate())
				return result;

			AttributeValue value = result.getAttributeValue();
			boolean argBooleanValue = ((BooleanAttribute) value).getValue();

			switch (getFunctionId()) {
			case ID_OR:
				if (argBooleanValue)
					return EvaluationResult.getTrueInstance();
				break;
			case ID_AND:
				if (!argBooleanValue)
					return EvaluationResult.getFalseInstance();
				break;
			}
		}

		if (getFunctionId() == ID_OR)
			return EvaluationResult.getFalseInstance();
		else
			return EvaluationResult.getTrueInstance();
	}
}
